In-vitro verification of the relative influence of condylar and incisal guidance on occlusion

Abstract

Objectives: The effects of condylar guidance on occlusion have been long discussed throughout the literature. Recently, simplified mounting technique by average setting the posterior component of occlusion has been advocated by some Prosthodontic clinician and this technique has been reported as clinically successful by several authors. However, the experimental explanation how average mounting offsets the consequence of deviation from individual condylar guidance is unclear yet. The purpose of this study was to verify the relative occlusal influence of condylar guidance compared to incisal guidance, and to examine the occlusal consequence of condylar guidance error during non-working side movement in articulator.

Materials and Methods: Three dimensional positions of non-working side maxillary 1st molar at different condylar and incisal settings were traced by use of laser displacement sensor attached on the motorized stages with biaxial freedom of movement. For the experiment, customized incisal pin andtable for arcon type Denar articulator were prepared. Incisal guidance was set at 0, 10, 20, 30, 40, 50, and 60 degree. Condylar guidance was set at 10, 20, 30, 40, and 50 degree. Respective contribution of the incisal and condylar guidance were analyzed by calculating multiple regression coefficient with resultant coordinate data.

Results: Relative influence of condylar and incisal guidance on vertical displacement of non-working side maxillary 1st molar were calculated as multiple regression coefficients of 0.431 and 0.881, respectively. Relative contribution of both guidance to lateral condylar inclination of non-working side maxillary 1st molar were calculated as multiple regression coefficients of 0.502 and 0.833, respectively. When non-working side excursion was limited to 1mm (along the X axis), difference between Z axis coordinate of 30 degree and that of less than 30 degree within the same incisal guidance setting varied from 172 to 1405 micrometer. Inter-examiner reliability indicated the experimental results to be within statistically highly reliable range.

Conclusion: There was difference in vertical position of maxillary right first molar during non-working side movement when condylar guidance setting varied. However, the incisal guidance had more effect over condylar guidance on vertical position and the lateral condylar inclination of the non-working side mandibular movement in articulator.